The long-term objective of this project is to understand how the olfactory system encodes information about odors. The olfactory system has a major role in regulating body hormonal state, emotional disposition, hunger, reproductive and social behavior. The work proposed here will advance understanding of the physiological processes, which subserve sensory function. Odors are received by olfactory receptor neurons in the olfactory epithelium of the nose and these receptor neurons convey the information to the main olfactory bulb in the brain, where they synapse onto mitral cells. The mitral cells process this information via neural circuits in the bulb and relay it to the primary olfactory or piriform cortex. The specific aims of this project are to measure the spontaneous activity of mitral cells, analyze temporal patterns and respiratory modulation of spontaneous action potentials, to correlate spontaneous activity with the impulse conduction velocity of mitral cells, and to investigate to what extent spontaneous activity in mitral cells is controlled by spontaneous activity in olfactory receptor neurons. Loss of the sense of smell is a common and debilitating problem. Acute loss may follow head trauma or environmental insult, while gradual loss often accompanies aging. Impaired olfaction compromises a person's ability to detect potential hazards such as smoke, gas leaks, and rancid food. Quality of life is also affected since most of the pleasure of food and drink comes from the nose. Increased knowledge of the normal and basic physiology of olfactory neurons is essential for developing strategies to treat olfactory deficits.